Biochemical, genetic, and epidemiologic characterization of Haemophilus influenzae biogroup aegyptius (Haemophilus aegyptius) strains associated with Brazilian purpuric fever

Abstract

Brazilian purpuric fever (BPF) is a recently recognized fulminant pediatric disease characterized by fever, with rapid progression to purpura, hypotensive shock, and death. BPF is usually preceded by purulent conjunctivitis that has resolved before the onset of fever. Both the conjunctivitis and RPF are caused by Haemophilus influenzae biogroup aegyptius (formerly called H. aegyptius). Isolates from 15 BPF cases, mainly from blood or hemorrhagic cerebrospinal fluid, case-associated isolates from 42 persons in towns where BPF cases occurred, and control strains from 32 persons in towns without BPF cases were characterized biochemically, genetically, and epidemiologically. Results indicated that a single clone was responsible for all BPF cases identified in six Brazilian towns from 1984 through 1986. All of 15 (100%) case strains were the same clone as was 1 of 32 (3%) control strains (P = <10-8). Isolates of the clone were preferentially intrarelated by DNA hybridization (99% relatedness, hydroxyapatite method at 60 and 75°C) and were separable from other H. influenzae biogroup aegyptius strains (approximately 90% relatedness at 60°C and 82% relatedness at 75°C). All isolates of the BPF clone and no other strains contained a 24-megadalton plasmid of restriction endonuclease type 3031, were of a single multilocus enzyme mobility type, were of a single sodium dodecyl sulfate-polyacrylamide gel electrophoresis type, and were in one of two ribosomal DNA restriction patterns. Ail BPF clone isolates reacted with monoclonal antibodies produced from a case strain; only 3 of 62 (5%) other strains reacted with this monoclonal antibody. Ninety percent of BPF clone strains and 27% of other strains were relatively resistant to sulfamethoxazole-trimethoprim.

Emergence and Disappearance of a Virulent Clone of Haemophilus influenzae Biogroup aegyptius, Cause of Brazilian Purpuric Fever

“…The BPF clone was susceptible to many commonly used antibiotics, including ampicillin, cefuroxime, cefotaxime, rifampin, and chloramphenicol (11). In the Serrana outbreak, the initiation of parenteral antibiotics before the development of hemorrhagic skins lesions was associated with better survival (10).…”

“…In addition, DNA hybridization studies indicated that the two organisms are phylogenetically a single species (2). To account for both the clinical and phenotypic differences, as well as the phylogenetic similarities, the name H. influenzae biogroup aegyptius has been assigned to what was previously known as H. aegyptius (11). For both simplicity and historical reasons, however, we refer to the organism as H. aegyptius throughout this review.…”

“…The primary cell surface antigen detected in this assay was determined to be the 25-kDa protein. The utility of this test was that it could be used to rapidly identify the BPF clone with a sensitivity and specificity of 100% and 85%, respectively (11). However, to improve on the specificity of this assay, a sandwich enzyme immunoassay was developed using BPF clone-specific immunoglobulin G2b (IgG2b) and IgM monoclonal antibodies.…”

“…Early in the BPF outbreak investigations, it became clear that the 3031 plasmid was present in BPF strains but not other strains of H. aegyptius (9). To determine the association of this plasmid with BPF, isolates from the following three groups of patients were compared: BPF case patients (group A), patients with conjunctivitis but not BPF but who were epidemiologically associated with BPF cases (group B), and patients with conjunctivitis that were not associated with BPF (group C) (11). The group A strains had been isolated from blood, cerebrospinal fluid, conjunctiva, and oro- pharynx.…”

“…There are four ST 65 isolates that have been submitted to the H. influenzae MLST website, all BPF clone isolates from São Paulo State, including one blood isolate from Valparaíso that lacks the 3031 plasmid (http://haemophilus.mlst.net/, last accessed August 8, 2008) (11,59) (Table 7 and Fig. 4).…”